1. Field of the Invention
The present invention relates to a control network system that controls a control object by a host system acquiring control data that is transmitted by a wireless field device in a wireless communication through a relay unit. More specifically, the present invention relates to a reduction of influence to a process by a wireless field device in commissioning.
Priority is claimed on Japanese Patent Application No. 2010-017544, filed Jan. 29, 2010, the content of which is incorporated herein by reference.
2. Description of the Related Art
All patents, patent applications, patent publications, scientific articles, and the like, which will hereinafter be cited or identified in the present application, will hereby be incorporated by reference in their entirety in order to describe more fully the state of the art to which the present invention pertains.
Conventionally, when a commissioning of the wireless field device connected to a distributed control system in a wireline connection is performed, adjustment/confirmation of the wireless field device is completed before the wireless field device is connected to the distributed control system. In other words, “confirmation before installation” is performed. Then, after the wireless field device is connected to the distributed control system, a final confirmation such as a feedback control loop check of PID control etc. is performed. The wireline connection is performed by an analog transmission as using a 4-20 mA analog signal or a digital transmission in accordance with the standard by the fieldbus association. The final confirmation is hereinafter referred to as commissioning.
In addition, for example, there are various wireless field devices such as a differential pressure gauge, a flowmeter, a thermometer, a monitor camera, an actuator, and a controller.
Recently, in the field of process control, technology to change a wireline transmission path to a wireless communication has been established. In particular, a constitution to connect a wireless field device by using a wireless transmission system represented by the ISA100.11a standard is examined. A wireless field device performing wireless communication in the above-described way is hereinafter referred to as a wireless field device. For example, a process control system of industrial automation is constituted by using a wireless control network system that includes a wireless field device. The conventional control system is constituted as a wireline network. Therefore, there is a limitation in communication distance and a limitation in guidance of wiring. Therefore, the sensor measuring temperature or flow quantity cannot be installed in the most suitable position in a plant. In addition, control precision is decreased.
As a wireless communication standard, wireless HART and a wireless communication standard for process control, ISA100.11a are examined. Wireless HART is regulated in HART (Highway Addressable Remote Transducer) 7. ISA100.11a was approved in ISA100 committee of ISA (International Society of Automation). WirelessHART and ISA100.11a are protocols/standards of wireless communication for industry to perform frequency division communication. “Wireless systems for industrial automation: Process control and related applications” discloses the contents of decisions of the above-described communications. Also, control with WirelessHART (URL:
http://www.hartcomm.org/protocol/training/resources/wiHART_resources/Control_with_WirelessHART.pdf) discloses the contents of decisions of the above-described communications.
Various wireless field devices are used as a field-set instrument in a process control system and a wireless control network system. There are wireless field devices such as a sensor or a control instrument measuring various physical quantities such as temperature, pressure, and flow quantity used in a measurement control field in the process control system.
Japanese Unexamined Patent Application, First Publication No. 2004-128785 discloses the above-described control network system.
In a conventional control network system that uses a wireline connection, even if one wireless field device has adjustment defects, influence of the adjustment defects to the plant can be prevented by detaching the wireless field device having adjustment defects. In a conventional control network system that uses a wireless connection, even if one wireless field device has adjustment defects, it is not easy to separate the wireless field device that is connected from the network. In adjustment confirmation before installation, a wireless network can be divided logically by using a network ID that is different from a network ID in the plant operation. A change of the network ID needs re-setting of the network ID to the wireless field device. The final confirmed state in the commissioning after connection needs to be reconfirmed. Because a different network is adjacent, wireless electric wave interference occurs, and performance decline that is different from the normal state may occur. The process is influenced by this performance decline. When connected using the same network ID, the process is influenced by the wireless field device of the non-steady state in the commissioning.